Investigations of rare earth and radioactive elements in black sands of Kerala Beach using spectroscopic techniques

The present manuscript deals with the identification of the spectral lines of the rare earth elements (REEs) in the LIBS spectra of the black sands collected from the Thiruvananthapuram (Kerala) beach using laser-induced breakdown spectroscopy (LIBS). LIBS spectra of the sand sample show the presence of spectral lines of Na, Mg, Mn, Al, and Cr. Along with these elements, the spectral lines of REEs such as Ce, Nd, Sm, Dy, Ho, Tm, etc., and the radioactive element Thorium (Th) are also present in the LIBS spectra of the black sand sample. The presence of REEs and radioactive elements makes the sand suitable for profitable extraction using various methods for different applications. The results of LIBS (presence of all REEs in sand) are also verified by photoacoustic spectroscopy (PAS). The Plasma temperature has been calculated using the Boltzmann plot to explain the distribution of the atoms in various higher energy states/levels. An attempt is made to explain the various transitions involved in the spectral lines of the rare earth ions in the LIBS spectra of the black sand sample using a possible energy level diagram. The concentration of some REEs (Dy, Sm, and Nd) and LOD has been calculated by using the calibration curve method. To the best of our knowledge, the investigation of rare earth and radioactive elements in the black sand of the Kerala beach using LIBS is reported for the first time.